To achieve data redundancy, database systems store data backups as well as write-ahead log backups in tertiary storage. Even in catastrophic situations, the database can be recovered from backup by using the last data backup and applying operations in backed-up database logs starting from this backup. In cases in which the database log in a log area is still available, it can be possible to recover all data up to the last commit.
Sometimes, a database administrator cannot or does not want to recover all data, but rather wants to recover data up to a specified point in time. This is, for instance, needed if some data was inadvertently removed from the database—the administrator can recover the database up to the time before the data has been removed. The administrator may also need to iteratively find a suitable point-in-time until which data recovery should be performed or, later, a new point-in-time recovery has to be performed and the like. At all times, backup history should not be lost, in order to enable recovery from any past backup.